Method and apparatus for liquefying gases



Filed Oct. 29, 1952 A INVENTOR 05022! /w I BY M QRNEY I tid/.ula

United States Patent O METHOD AND APPARATUS FOR LIQUEFYING GASES RobertSpitzer, New York, N. Y., assignor to M. H. Treadwell Co., Inc., NewYork, N. Y., a corporation of New York Application October 29, 1952,Serial No. 317,454

7 Claims. (Cl. 62-122) This invention relates to the liquefaction ofgases and more particularly to the liquefaction of chlorine. While theinvention is described hereinafter chiefly in connection with theliquefaction of chlorine, it will be understood it is not limitedthereto and includes the liquefaction of other gases. In thespecitication and claims, all pressures are absolute.

Chlorine gas is produced in electrolytic cells at a pressure about orjust below atmospheric pressure, usually a pressure of from 1/2 to 11/2inches of water below atmospheric pressure. Heretofore this chlorine gashas been liquefied by compressing the dried gas to a pressure of from 20pounds per square inch to 165 pounds per square inch and cooling to atemperature of from 55 F. to 70 F., respectively. Various types ofcompressors have been used, such, for example, as sulfuric acidlubricated piston compressors, carbon ring compressors, sulfuric acidring compressors and diaphragm compressors. However, due to thecorrosive nature of the gases handled, the operation of thesecompressors invariably presents diiculties and their mechanicaleiciencies are relatively low.

It is among the objects of this invention to provide a process forliquefying chlorine and other gases, which process does not involve theuse of a compressor for compressing the gas and which process, exceptfor the valves employed to control flow, does not require for itspractice mechanism having moving parts which come into contact with thegas or the liqueed gas.

Another object of this invention is to provide a process for liquefyinggases, including chlorine, which process is ecient in practice andeconomical to carry out.

Still another object of this invention is to provide an arrangement ofapparatus for practicing the process of this invention which arrangementis compact, simple, eficient in operation and relatively inexpensive tomaintain.

Other objects and advantages of this invention will be apparent from thefollowing detailed description thereof.

In accordance with this invention a stream of chlorine gas at or belowatmospheric pressure is mixed with a stream of chlorine vapor. undersuperatmospheric pressure and produced by vaporizing liquid chlorine.There is thus produced a stream of chlorine gas under pressure. Thisstream is cooled to condense at least that portion of the chlorine gaswhich corresponds in amount to the amount of chlorine vapor admixed withthe incoming chlorine gas stream. A portion of the chlorine liquid thusproduced is vaporized to produce the stream of chlorine vapor u nderpressure employed to compress the chlorine gas. The remainder of thechlorine liquid may be withdrawn as product.

When liquefymg a chlorine gas containing incondensables, such as air,carbon dioxide and hydrogen, and it isV desired to eifect substantiallycomplete condensation of the chlorine, a two stage condensationprocedure should preferably be employed.

A one stagecondensation procedure, such as that hereinabove described,may be used to effect substantially ICC complete condensation of purechlorine or partial condensation of chlorine when liquefying a chlorinegas containing incondensables. In the use of a two stage condensationprocedure, the uncondensed chlorine gas from the lrst condensation stageis passed through a second stage where the residual chlorine gas iscondensed. Desirably, the second stage of the condensation orliquefaction is carried out by passing a portion of the liquid chlorineunder pressure from the irst stage through a heat interchanger where theliquid is cooled by chlorine gas flowing in heat exchange relationshiptherewith. The thus cooled chlorine liquid under pressure is thenexpanded creating refrigeration which is employed to effect thecondensation of the chlorine in the second stage. The expanded chlorinegas is employed to pre-cool the chlorine liquid in the aforesaid heatinterchanger. In this way condensation of the chlorine is effected mostefliciently.

The accompanying drawing shows for purposes of exempliiication apreferred layout of equipment for practicing the process of thisinvention. It will be understood this invention is not limited to thearrangement of equipment shown in the drawing.

In the drawing 10 indicates a vapor injector of any well known typewhich may be a single or multistage injector. This injector communicatesthrough a line 11 with a source of chlorine gas which may be atatmospheric pressure or slightly below atmospheric pressure. Forexample, line 11 may communicate with a collector main receivingchlorine from electrolytic chlorine generating cells. A line 12 connectsvapor injector 10 with a vaporizer 13. A valve 14 desirably operated bya pressure controller 15 of any conventional type and which isresponsive to the pressure in the feed line 11 controls the supply ofchlorine vapor under a predetermined pressure to the vapor injector 10.The stream of chlorine vapor under pressure flowing through injector 10effects flow of chlorine gas through line 11 into the vapor injector.The chlorine vapor thus supplied by the vaporizer 13 desirably is at apressure within the range of from to 1000 pounds, preferably at about1000 pounds, per square inch.

The vaporizer 13 may be of any well known type, such, for example, as anevaporator arranged to receive steam under pressure from a line 16,which steam passes in indirect heat exchange relation with liquidchlorine supplied to the vaporizer by means of a line 17 communicatingwith an injector 18, which in turn communicates through a line 19 withthe vaporizer 13. As customary, the vaporizer 13 may be provided with atrap 20 equipped with a flow control valve 21 controlling flow ofcondensate from the vaporizer 13 and a purge line 22 for purging thevaporizer when desired.

In the embodiment shown in the drawing ilow of liquid chlorine to thevaporizer is accomplished by providing feed line 12 leading from thevaporizer with a branch 23, ow through which is controlled by a tloatvalve 24. This valve is responsive to the level of liquid within thevaporizer and is designed to maintain a body of liquid chlorine withinthe vaporizer at all times. In operation chlorine vapor under a desiredpredetermined pressure within the range of 100 to 1000 pounds per squareinch is recirculated through line 23, injector 18, line 19 and the upperportion of the vaporizer 13. This stream of chlorine vapor underpressure effects flow of iiquid chlorine through line 17 into thevaporizer where the liquid chlorine is heated by steam or other heatingmedium sup- `plied to the vaporizer 13 thus generating the chlorine in astream of chlorine gas leaving the vapor injector under a pressure offrom 50 to 250 pounds per square inch, preferably about 150 pounds persquare inch. It will be' understood that instead of supplying the liquidchlorine to the vaporizer 13 by means of an injector 18, a pump or othersuitable feed means may be employed to supply the liquid chlorine to thevaporizer 13.

From the injector 10 to the chlorine gas stream under pressure of from50 to 250 pounds per square inch flows through line into the first stagecondenser 26. This condenser may be of any well known indirect heatexchange type, cooled, for example, by water, air or other coolingmedium supplied through inlet 27. The cooling iediurn ows in indirectheat exchange relation with the mixture of chlorine gas passing throughcondenser 26 and exits through the outlet 28. Cooling of the cornpressedchlorine gas results in condensation of a portion of the gas; the amountof chlorine thus condensed should at least equal and preferably exceedthe amount of chlorine supplied to the vaporizer 13. The condensate, aswell as incondensables which may be present ows from condenser 26 into atank 29. The base of this tank communicates with line 17 leading to theinjector 18 here inabove described and also with a line 30 through whicha portion of the condensate from tank Z9 is supplied to a refrigeranteconomizer 31.

Economizer 31 is an indirect heat exchanger for flow of liquid chlorineunder pressure entering this economizer through line 345 and excitingthrough line 32. This liquid flows in indirect heat exchange relationwith chlorine gas entering through line 33 and exiting through line 34which communicates with the injector 10. Thus, injector 10 serves tocompress chlorine gas flowing thereto from both lines 34 and 11 in theembodiment of the invention shown in the drawing.

Overow condensate from tank 29, as well as uncondensed chlorine gas andincondensables flow from tank 29 through a line 35 into a second stagecondenser 36. This mixture ilows in indirect heat exchange relation withchlorine gas produced by expansion of the chlorine liquid flowing fromline 32 through iloat controlled expansion valve 37 which maintains adesired level of chlorine liquid in the second stage condenser. Flashingof the liquid to vapor produces refrigeration which is imparted to themixture flowing through the second stage condenser 36. From the secondstage condenser 36 the gas ows through iine 33 which communicates withthe economizer 31.

The condensate thus produced in condenser 36 and any incondensableswhich may be present leave this condenser through a line 39 whichcommunicates with a pair of product receiving tanks 40 and 41. Two tanksare provided so that one may be charged while the other is discharged.These tanks are provided with a suitable vent i2 through whichincondensables may be vented. A back pressure control valve 43 actuatedby controller 44 is provided to maintain the system under a desiredsuperatmospheric pressure. Tanks 40 and 41 are provided with suitablevalve controlled draw-ott lines 45 which communicate with a header 46.

The following example of liquefying chlorine in accordance with theprocess of this invention in the layout of equipment shown in theaccompanying drawing is given for purposes of illustration only. It willbe understood the invention is not limited to this example.

100 pounds of chlorine gas per hour at atmospheric pressure and atemperature of 80 F. and approximately 2 pounds incondensables chieyair, hydrogen and carbon dioxide are supplied to the vapor injector 10through line 11. 49.5 pounds of chlorine gas per hour at a ternperatureof 70 F. are also supplied to this vapor injector through line 44, thisgas having been employed to effect condensation in the second stagecondenser 36, as hereinafter more fully described. The resultant mixtureis compressed to a pressure of 150 pounds per square inch by 895 poundsof saturated chlorine vapor per hour supplied to the vapor injector 10from the vaporizer 13 under a pressure of 1000 pounds per square inch.1044.5 pounds of chlorine vapor and 2 pounds incondensables are thussupplied to the first stage condenser 26 where this mixture is cooled bywater which enters at a temperature of about 70 F. Approximately 75% ofthe incoming chlorine, as well as all of the chlorine (895 pounds perhour) supplied to the vaporizer 13, is condensed in the first stagecondenser.

The liquid chlorinecon'densate, as well as uncondensed vapor, enter thetank 29 which is under the system pressure of approximately 150 poundsper square inch. 895 pounds of liquid chlorine per hour are withdrawnfrom this tank and passed through line 17 into the injector 18, feed ofthis liquid chlorine being effected by the chlorine vapor circulatedthrough the line 23, Valve 24 and injector 13. 49.5 pounds per hour ofliquid chlorine at a temperature of F. iiows from the tank 29 throughline 30 into the economizer 31 where it is cooled to a temperature of 25F. by 49.5 pounds of chlorine gas per hour entering at a temperature of30 F. and leaving economizer 31 at a temperature of 70 F. This chlorinegas flows from the economizer 31 through line 34 into the injector 10.The cooled liquid chlorine at a temperature of 25 F. and a pressure of150 pounds per square inch tlows through the expansion valve 37 and isflashed into vapor at substantially atmospheric pressure. The resultantvapor tiows through the second stage condenser 36 in indirect heatexchange relation with the liquid chlorine, uncondensed chlorine andinerts passing through this condenser. This liquid mixture is thuscooled to a temperature of -25 F. at which temperature and under apressure of pounds per square inch it enters the storage tank 4.0 or 41;99.2 pounds of liquid chlorine per hour are thus fed into a storagetank.

If it is desired to liquefy 75 or less of the chlorine under the abovenoted conditions of chlorine concentration and temperature of coolingmedium supplied to the first stage condenser, this can be effectedemploying only the rst stage of condensation. In this event the secondstage condenser and associated economizer need not be employed, and,hence, may be omitted in installations designed to liquefy 75 or less ofthe chlorine under the above noted conditions. Thus, in those caseswhere 25% or more of the chlorine generated can be used in the gaseousphase and it is desired to liquefy 75% or less of the chlorinecontaining about 2% by volume of incondensables, the installationembodying this invention may involve only a single stage ofcondensation.

While the invention has been described above in connection with theliquefaction of chlorine it is not limited thereto. It may be employedin the liquefaction of other gases, such, for example, as ammonia (NH3),stibine (SbHs), arsenic pentauoride (AsFs), arsine (AsHs), carbontetratluoride (CF4), carbon dioxide (CO2), carbon oxysuliide (COS),chlorine monouoride (CIF), chlorine triuoride (ClFa) cyanogen (CzNz),fiuorine (F2), chlorotriuorogermane (GeFaCl), germanium monohydride(GeH), hydrogen bromide (HBr), hydrogen chloride (HCl), hydrogen uoride(HF), hydrogen iodide (HI), phosphine (HSF), hydrogen sulfide HzS),hydrogen telluride (HzTe), nitrous oxide (N20), nitrogen dioxide (NO2),nitrosyl chloride (NOCl), phosphorus triuoride (PFg), phosphorusoxyfluoride (POP3), radon (Rn), trifluoro silicane (SiHFa), silicontetrafluoride (SiFi), silane (Sil-i4), disilicane (SizHs),trisilicylamine ((SiH3)3N), sulfur tetrafluoride (SP4), sulfur dioxide(SO2), sulfuryl iiuoride (SOzFz), telluriam hexafluoride (TeFs),stannane (SnHi) uranium hexafluoride (UF6), and other liqueiiable gases.

It will be noted this invention provides a method of liquefyingliqueliable gases which eliminates the necessity of using compressorsfor compressing the gas and which is eicient in operation and economicalto carry out. It will be further noted the arrangement of apparatus forpracticing this invention is compact, simple to operate, ecient inoperation, and, hence, involves relatively small maintenance expenses.

Since certain changes may be made in carrying out the above describedembodiments of the invention without departing from its scope, it isintended that all matter contained in the above description shall beinterpreted as illustrative and not in a limiting sense. Thus, while inthe embodiment hereinabove described the chlorine gas which effectscooling in the second stage is expanded to atmospheric pressure, itcould be expanded to below this pressure. This would involve providingthe line 34 leading to the injector with a second injector to maintainsubatmospheric pressure conditions within line 34, economizer 31, line33 and the portion of condenser 36 through which the expanded gas flows.Also instead of supplying the gas to be liqueled at sub or atmosphericpressure it may be supplied at relatively low superatmosphericpressures.

Furthermore, the parts may be suitably insulated and arranged for mostecient heat exchange and optimum utilization of available heat andrefrigeration. Thus, for example, the liquid chlorine flowing throughline 19 may be passed in heat exchange relation with the chlorine gasstream ilowing through line 25 to precool the chlorine gas entering thecondenser 26 and warm the chlorine liquid entering the vaporizer 13.

What is claimed is:

1. A method of liquefying chlorine gas containing incondensables fromthe group consisting of air, carbon dioxide and hydrogen and atapproximately atmospheric pressure, which method comprises step 1,vaporizing liquid chlorine obtained from step 4 to produce a stream ofchlorine vapor under pressure; step 2, passing said stream of chlorinevapor under pressure through an injector communicating with the chlorinegas to be liquefied and with chlorine gas coming from step 6 and thusproducing a stream of chlorine gas under pressure containing saidincondensables; step 3, cooling the stream from step 2 to condense themajor portion but not all of the chlorine gas; step 4, dividing theliquid chlorine from step 3 into three streams, one of which is employedin step 1 of the process; step 5, cooling another of the streams ofliquid chlorine from step 4 containing chlorine gas not condensed instep 3 and said incondensables to eect condensation of the residualchlorine gas, withdrawing the chlorine condensate thus produced from theprocess as product and venting the incondensables from the process; andstep 6, expanding the third stream of liquid chlorine from step 4 toproduce refrigeration which is employed to efect the cooling in step 5and passing the chlorine gas thus produced to step 2 of the process.

2. A method of liquefying a liqueable gas under approximatelyatmospheric pressure which method comprises step 1, vaporizing a portionof the liquefied gas obtained from step 4 to produce a vapor streamunder pressure; step 2, passing said vapor stream under pressure throughan injector communicating with the gas to be liqueed and with the gascoming from step 6 and thus producing a stream of gas under pressure;step 3, cooling said stream from step 2 to condense an amount thereof atleast equal to the amount of gas vapor produced in step 1, but not allof said stream; step 4, dividing the condensate from step 3 into threestreams one of which is utilized in step 1 of the process; step 5,cooling the second stream of condensate from step 4 along withuncondensed constituents from step 3 to condense uncondensedconstituents and withdrawing from the process the condensate produced instep 5 as the liqueed gas product; and step 6, expanding the thirdstream of condensate from step 4 to produce refrigeration which isemployed to effect the cooling in step 5 and passing the gas produced byexpanding said third stream of condensate to step 2 of the process.

3. A method of liquefying chlorine which comprises step 1, vaporizingliquid chlorine obtained from step 4 to produce a stream of chlorinevapor under pressure; step 2, passing said stream of chlorine vaporunder pressure through an injector communicating with chlorine gas to beliquefied and with chlorine gas coming from step 6 and thus producing astream of chlorine gas under pressure; step 3, cooling the stream fromstep 2 to condense the major portion but not all of the chlorine gas;step 4, dividing the liquid chlorine from step 3 into three streams, oneof which is employed in step 1 of the process; step 5, cooling anotherof the streams of liquid chlorine from step 4 along with chlorine gasnot condensed in step 3 to elfect condensation of said chlorine gas; andstep 6, expanding the third stream of condensate from step 4 to producerefrigeration which is employed to eiTect the cooling in step 5 andpassing the chlorine gas thus produced to step 2 of the process.

4. The method defined in claim 3, in which the chlorine vapor generatedin step 1 is at a pressure of from 100 to 1000 pounds per square inch,the mixed stream produced in step 2 is at a pressure of about 150 poundsper square inch and the chlorine liquid in step 6 is expanded from apressure of about pounds per square inch to atmospheric pressure.

5. The method dened in claim 3, in which in step 6 the third stream ofliquid chlorine condensate is precooled by passage in indirect heatexchange relation with chlorine gas, the thus cooled condensate isexpanded to produce chlorine gas, this chlorine gas is employed to eiectthe cooling of step 5 by owing in indirect heat exchange relation withthe material which is cooled in step 5 and this chlorine gas isthereafter employed to effect said precooling of the said third streamof liquid chlorine condensate and then passed to the injector in step 2of the process.

6. The method dened in claim 3, in which a portion of the vapor producedin step 1 is passed through an injector communicating with the stream ofchlorine liquid which is vaporized to produce the chlorine vaporemployed in step 1 of the process and thus eects ow of said chlorineliquid into the vaporizer.

7. Apparatus for liquefying gases, in combination, a vaporizer, aninjector, a line connecting said vaporizer with said injector for ow ofvapors from said vaporizer to said injector, a iirst condenser, a secondcondenser, a heat interchanger, a line leading from said heatinterchanger to said injector, a second line for supplying the gas to beliquefied to said injector, means leading from said first condenser tosaid vaporizer and including an injector for etfecting flow ofcondensate from said first condenser to said vaporizer by circulation ofvapors generated in said vaporizer through said second-mentionedinjector, and means connecting said rst condenser with said secondcondenser, said condensers and heat interchanger being constructed andarranged for iow of a portion of the liquid condensate produced in therst condenser through the heat interchanger where it is cooled, thenthrough an expansion valve into the second condenser where it is flashedinto vapor, which is passed from the second condenser through the heatinterchanger and thence to the first-mentioned injector.

References Cited in the file of this patent UNITED STATES PATENTS1,014,120 Coleman Jan. 9, 1912 1,073,843 Blau Sept. 23, 1913 1,497,546Claude .lune 10, 1924 1,913,268 Falkenberg June 13, 1933 1,945,367Gobert Jan. 30, 1934 1,972,705 Crosthwait Sept. 4, 1934 2,014,701Seligman Sept. 17, 1935 2,035,814 Kallam Mar. 31, 1936 2,166,191 WhitneyJuly 18, 1939 2,174,302 Whitney Sept. 26, 1939 2,568,223 De Baufre Sept.18, 1951 2,637,174 Austin May 5, 1953

1. A METHOD OF LIQUEFYING CHLORINE GAS CONTAINING INCONDENSABLES FROMTHE GROUP CONSISTING OF AIR, CARBON DIOXIDE AND HYDROGEN AND ATAPPROXIMATELY ATMOSPHERIC PRESSURE, WHICH METHOD COMPRISES STET 1,VAPORIZING LIQUID CHLORINE OBTAINED FROM STEP 4 TO PRODUCE A STREAM OFCHLORINE VAPOR UNDER PRESSURE; STEP 2, PASSING SAID STREAM OF CHLORINEVAPOR UNDER PRESSURE THROUGH AN INIECTOR COMMUNICATING WITH THE CHLORINEGAS TO BE LIQUEFIED AND WITH CHLORINE GAS COMING FROM STEP 6 AND THUSPRODUCING A STREAM OF CHLORINE GAS UNDER PRESSURE CONTAINING SAIDINCONDENSABLES; STEP 3, COOLING THE STREAM FROM STEP 2 TO CONDENSE THEMAJOR PORTION BUT NOT ALL OF THE CHLORINE GAS; STEP 4, DIVIDING THELIQUID CHLORINE FROM STEP 3 INTO THREE STREAMS, ONE OF WHICH IS EMPLOYEDIN STEP 1 OF THE PROCESS; STEP 5, COOLING ANOTHER OF THE STREAMS OFLIQUID CHLORINE FROM STEP 4 CONTAINING CHLORINE GAS NOT CONDENSED INSTEP 3 AND SAID INCONDENSABLES TO EFFECT CONDENSATION TO THE RESIDUALCHLORINE GAS, WITHDRAWING THE CHLORINE CONDENSATE THUS PRODUCED FROM THEPROCESS AS PRODUCT AND VENTING THE INCONDENSABLES FROM THE PROCESS; ANDSTEP 6, EXPANDING THE THIRD STREAM OF LIQUID CHLORINE FROM STEP 4 TOPRODUCE REFRIGERATION WHICH IS EMPLOYED TO EFFECT THE COOLING IN STEP 5AND PASSING THE CHLORINE GAS THUS PRODUCED TO STEP 2 OF THE PROCESS.